Here is what I did:

6 10' lengths of 3/4" pvc from HD ($4 per length) and 5 unions glued together. You can push 1/2" staset-X into the pvc or use an electrical tape. Roll the mast so the exit/sheave are low and slide the pvc in. Once you capture the halyard at the top you can pull the pvc out and fish the other end through the exit. It was relatively easy to see where the pvc goes and it will stay straight. The fish tape will not.